Zeolite L

ABSTRACT

A zeolite related to zeolite L and having a characteristic cylindrical morphology may be prepared from a crystallization gel comprising (in mole ratios of oxides): 
     K 2  O/SiO 2  : 0.22-0.36 
     H 2  O/K 2  O: 25-90 
     SiO 2  /Al 2  O 3  : 6-15 
     and preferably with the mole ratio H 2  O/K 2  O+Al 2  O 3  +SiO 2  being at least 8. The cylindrical Zeolite L may be used as a catalyst base in aromatization of acyclic hydrocarbons with high benzene yields being sustained over commercially feasible periods.

This is a division, of application Ser. No. 493,688; filed May 11, 1983,now U.S. Pat. No. 4,544,539.

This invention relates to a highly crystalline zeolite material, itspreparation and use in catalysis, particularly for aromatization. Inparticular it relates zeolite L with cylindrical morphology.

Zeolite L has been known for some time as an adsorbant, and in U.S. Pat.No. 3,216,789 is described as an aluminosilicate of the formula:

    0.9-1.3M.sub.2/n O:Al.sub.2 O.sub.3 :5.2-6.9SiO.sub.2 :yH.sub.2 O

(where M is an exchangeable cation of valence n and y is from 0 to 9)having an X-ray diffraction pattern with the following more significantd(Å) values:

16.1±0.3

7.52±0.04

6.00±0.04

4.57±0.04

4.35±0.04

3.91±0.02

3.47±0.02

3.28±0.02

3.17±0.01

3.07±0.01

2.91±0.01

2.65±0.01

2.46±0.01

2.42±0.01

2.19±0.01

The preparation of zeolite L described in U.S. Pat. No. 3,216,789comprises crystallizing the zeolite from a reaction mixture comprisingmole ratios:

K₂ O/(K₂ O+Na₂ O): 0.33-1

(K₂ O+Na₂ O)/SiO₂ : 0.35-0.5

SiO₂ /Al₂ O₃ : 10-28

H₂ O/(K₂ O+Na₂ O): 15-41

The silica to alumina ratio in this reaction mixture is significantlyhigher than the ratio in the formed zeolite.

British Pat. No. 1 202 511 describes a revised zeolite L preparationusing lower proportions of silica in the reaction mixture whichcomprises mole ratio of reactants as:

K₂ O/(K₂ O+Na₂ O): 0.7-1

(K₂ O+Na₂ O)/SiO₂ : 0.23-0.35

SiO₂ /Al₂ O₃ : 6.7-9.5

H₂ O/(K₂ O+Na₂ O): 10.5-50

The ratio H₂ O/(K₂ O+Na₂ O+SiO₂ +Al₂ O₃) is preferably not greater than6 to give a "dry gel".

U.S. Pat. No. 3,867,512 discloses a preparation of zeolite L from areaction mixture having a molar composition:

K₂ O/(K₂ O+Na₂ O): 0.3-1

(K₂ O+Na₂ O)/SiO₂ : 0.3-0.6

SiO₂ /Al₂ O₃ : 10-40

H₂ O/(K₂ O+Na₂ O): 15-140

in which the silica source is a gel having at least 4.5 weight percentwater and prepared in a particular manner.

L Wilkosz in Pr Chem 409 (1974)--Chemical Abstracts, vol 90 (1979)573478 describes the preparation of zeolite L from a synthesis solprepared by treating a solution containing silica, potassium hydroxideand sodium hydroxide with a second solution containing potassiumaluminate, potassium hydroxide and sodium hydroxide and crystallizingfor 72 hours at 20° C. and 122 hours at 100° C. The zeolite L producthas a SiO₂ :Al₂ O₃ ratio of 6.4:1.

G V Tsitsishvilli et al in Doklady Akademii NaukSSSR, Vol 243, No 2,pp438-440 (1978) describe the synthesis of zeolite L from alumina-silicagels containing tributylamine. The gels used had the following molarratios:

SiO₂ :Al₂ O₃ : 25

(K₂ O+Na₂ O):Al₂ O₃ : 18

(K₂ O+Na₂ O):SiO₂ : 0.72

H₂ O/K₂ O+Na₂ O: 20

K₂ O:Na₂ O: 0.5

Y Nishiimura in Nippon Kagaku Zasshi 91, 11, 1970, pp 1046-9 describesin general terms zeolite L preparation from a synthesis mixturecontaining colloidal silica, potassium aluminate and potassium hydroxidehaving a SiO₂ :Al₂ O₃ ratio of 15-25, but exemplifies only two synthesismixtures having the following ratios of components:

7K₂ O:Al₂ O₃ :20SiO₂ :450H₂ O; and

8K₂ O:Al₂ O₃ :10SiO₂ :500H₂ O.

Frety et al in C R Acad Sc Paris, t275, Serie C-1215 describes theelectron microscope examination of zeolite L in which particles weresaid to be observed in the form of slightly deformed cylinders with veryvariable dimensions.

U.S. Pat. No. 3,298,780 describes zeolite UJ having a composition,expressed as mole ratios of oxides, corresponding to 0.9±0.2R_(2/v)O:Al₂ O₃ :5.0±1.5SiO₂ :wH₂ O wherein R represents at least one cationhaving a valence of not more than 4, v represents the valence of R and wcan be any value up to about 5, said zeolite having an X-ray powderdiffraction pattern essentially as shown in the following table:

    ______________________________________                                        Interplanar spacing, d(Å)                                                                  Relative Intensity                                           ______________________________________                                        16.25 ± 0.25  VS                                                           7.55 ± 0.15   M                                                            6.50 ± 0.10   M                                                            5.91 ± 0.10   W                                                            4.61 ± 0.05   S                                                            3.93 ± 0.05   S                                                            3.67 ± 0.05   W                                                            3.49 ± 0.05   M                                                            3.29 ± 0.05   W                                                            3.19 ± 0.05   M                                                            3.07 ± 0.05   M                                                            2.92 ± 0.05   M                                                            2.66 ± 0.05   W                                                            ______________________________________                                    

prepared by a process comprising preparing an aqueous reactant solutionhaving a composition, expressed as mole ratios of oxides, correspondingto

SiO₂ /Al₂ O₃ of from 6 to 30,

R_(2/v) O/SiO₂ of from 0.30 to 0.70, and

H₂ O/R_(2/v) O of from 80 to 140;

and maintaining said reactant solution at a temperature between 150° F.(65.6° C.) and 325° F. (162.8° C.) until the zeolite crystals areformed. Zeolite UJ is described as having nearly cubic shaped crystalswith a crystal size ranging upward from 0.05 micron.

GB 1 393 365 describes zeolite AG1, related to zeolite L, having themolar composition other than water:

    1.05±0.3M.sub.2 O:Al.sub.2 O.sub.3 :4.0-7.5SiO.sub.2

wherein M is potassium or a mixture of potassium and sodium, and anX-ray powder diffraction pattern substantially as set forth in Columns Iand II of the following table, and capable of adsorbing at least 3% w/wperfluorotributylamine.

    ______________________________________                                        COLUMN I               COLUMN II                                              Potassium              Potassium/sodium                                       zeolite AGl            zeolite AGl                                                    Relative               Relative                                       d(Å)                                                                              intensity      d(Å)                                                                              Intensity                                      ______________________________________                                        15.85   36.9           15.78   37.5                                           --      --             --      --                                             7.53    8.5            7.50    10                                             6.00    9.5            6.00    10                                             --      --             5.86    7                                              5.75    6              --      --                                             4.61    24             4.59    28                                             4.40    7              4.40    7                                              4.35    5              --      --                                             3.93    31             3.91    35                                             --      --             --      --                                             3.66    13             3.65    17                                             3.48    17             3.47    23                                             3.27    13             3.27    17                                              3.186  29             3.18    31.5                                           3.07    20             3.07    24                                             3.01    9.5            --      --                                             2.91    21.5           2.91    28                                             2.65    15.5           2.65    18.5                                           --      --             --      --                                             --      --             2.50    6                                              2.49    5              --      --                                             2.46    3              2.46    5                                              2.42    3              2.42    4                                              2.19    8              2.19    12                                             ______________________________________                                    

Zeolite AG1 is described as being prepared by reacting at least onealuminium component, at least one silicon component and at least onealkali metal component, in an aqueous medium, the sole or major siliconcomponent being a water glass having a molar ratio SiO₂ /M₂ O of 3.5 to4.0 to give a reaction mixture with oxide molar ratios in one of thefollowing ranges:

    ______________________________________                                        Range 1     SiO.sub.2 /Al.sub.2 O.sub.3                                                                   7-14                                                          (K.sub.2 O + Na.sub.2 O)/SiO.sub.2                                                           0.25-0.85                                                      K.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                           0.75-1.0                                                       H.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                            25-160                                            Range 2     SiO.sub.2 /Al.sub.2 O.sub.3                                                                  14-20                                                          (K.sub.2 O + Na.sub.2 O)/SiO.sub.2                                                           0.25-0.85                                                      K.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                           0.5-1.0                                                        H.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                            25-160                                            Range 3     SiO.sub.2 /Al.sub.2 O.sub.3                                                                  20-40                                                          (K.sub.2 O + Na.sub.2 O)/SiO.sub.2                                                           0.25-1.0                                                       K.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                           0.4-1.0                                                        H.sub.2 O/(K.sub.2 O + Na.sub.2 O)                                                            25-160                                            ______________________________________                                    

It was subsequently found that zeolite L may be used as a catalyst basein aromatization reactions. U.S. Pat. No. 4,104,320 disclosesdehydrocyclization of aliphatic compounds in the presence of hydrogenusing a catalyst comprising zeolite L and a group VIII metal, in whichthe zeolite L is of the formula:

    M.sub.9/n (AlO.sub.2).sub.9 (SiO.sub.2).sub.27

(where M is a cation of valence n) but the silica to alumina ratio mayvary from 5 to 7. Zeolite L is described as occuring in the form ofcylindrical crystals a few hundred Angstroms in diameter.

East German Pat. No. 88789 discloses dehydrocyclization using a catalystformed from a zeolite precursor with a silica to alumina ratio of 5 orgreater which is dealuminised to give a silica to alumina ratio of up to70. Zeolite L is mentioned as a precursor.

European Patent Application Publication 40119 discloses adehydrocyclization process operating at low pressure (1 to 7 bars) orlow H₂ /hydrocarbon ratio using a catalyst comprising platinum on apotassium zeolite L. BE 888365 describes dehydrocyclization using acatalyst comprising platinum, rhenium (incorporated in the form of itscarbonyl) and sulphur to give an atomic ratio of sulphur to platinum of0.05 to 0.6 on a zeolitic crystalline aluminosilicate base such aszeolite L. BE 792608 discloses the treatment of zeolite L for use ascatalyst in isomerization by exchange with ammonium and chromium ions.

It has now been found that a new zeolitic material having some similarcharacteristics to zeolite L, but having a characteristic morphology andsize is particularly valuable for use as a catalyst base in hydrocarbonconversions such as aromatization.

Thus, in one aspect this invention concerns a zeolite having an X-raydiffraction (XRD) pattern obtained with CuKα radiation having thefollowing significant d (Å) values:

                  TABLE A                                                         ______________________________________                                        16.1 ± 0.4                                                                 7.52 ± 0.05                                                                6.00 ± 0.04                                                                4.57 ± 0.04                                                                4.35 ± 0.04                                                                3.91 ± 0.02                                                                3.47 ± 0.02                                                                3.28 ± 0.02                                                                3.17 ± 0.02                                                                3.07 ± 0.02                                                                2.91 ± 0.02                                                                2.65 ± 0.02                                                                2.46 ± 0.02                                                                2.42 ± 0.01                                                                2.19 ± 0.01                                                                ______________________________________                                    

and comprising crystallites in the form of cylinders with a meandiameter of at least 0.1 micron. The above XRD lines characterize thezeolite of the invention and correspond to those identified ascharacteristic of zeolite L in U.S. Pat. No. 3,216,789. The spectrum ofthe zeolite of the invention will also generally show additional lines,and more complete listings of the d (Å) values for specific materials ofthe invention are given hereinafter. In general the ten most prominentpeaks in the XRD pattern of the materials of the invention are given inTable B below:

                  TABLE B                                                         ______________________________________                                        16.1 ± 0.4                                                                 4.57 ± 0.04                                                                3.91 ± 0.02                                                                3.66 ± 0.02                                                                3.47 ± 0.02                                                                3.28 ± 0.02                                                                3.17 ± 0.02                                                                3.07 ± 0.02                                                                2.91 ± 0.02                                                                2.65 ± 0.02                                                                ______________________________________                                    

The positions and relative intensites of the X-ray lines are found tovary only slightly with changes in the cation form of the materials.However, the intensity of the line at d=16.1±0.3 Å has been observed tobe more variable than that of other prominent lines. This is believed tobe a result of the sensitivity of this peak to the preparation of theXRD sample and not to significant changes in crystal structure of thezeolite. Occasionally, additional lines not belonging to the pattern forzeolite L appear in a pattern along with the X-ray lines characteristicsof the zeolite. This is an indication that one or more additionalcrystalline materials are mixed with zeolite L in the sample beingtested. It is a preferred feature of the invention that the amount ofsuch additional crystalline materials is minimised in the zeolitematerial as synthesized. In particular, as discussed in more detailhereinafter, it is preferred that the synthesis of the zeolite of theinvention is conducted so that the amount of zeolite W in the product ofthe synthesis is minimised. Further, the synthesis of the zeolite of theinvention is preferably conducted such that the product of the synthesisis substantially free of any additional crystalline phase giving rise toa line in the X-ray pattern at d (Å) value of 6.28±0.05.

The particular X-ray technique and/or apparatus employed, the humidity,the temperature, the orientation of the crystals in the sample and othervariables, all of which are well known and understood to those skilledin the art of X-ray crystallography or diffraction, may also cause somevariations in the positions and intensities of the X-ray lines. Thus,the X-ray data given herein to identify the zeolites of the inventionare not to exclude those materials which, due to some variable mentionedabove or otherwise known to those skilled in the art fail to show all ofthe tabulated X-ray lines, or show a few extra ones that are permissibleto the crystal system of the zeolite, or show a shift in position orslight change in intensity of some of the X-ray lines.

The zeolites of the invention are preferably aluminosilicates and willbe described hereinafter in terms of aluminosilicates, though otherelemental substitutions are possible, for example aluminium may besubstituted by gallium, boron, iron and similar trivalent elements, andsilicon may be substituted by elements such as germanium or phosphorus.The aluminosilicates preferably have a composition (expressed in termsof molar ratios of the constituent oxides in anhydrous form) of:

    (0.9-1.3)M.sub.2/n O:Al.sub.2 O.sub.3 :xSiO.sub.2

(I)

wherein M is a cation of valence n, x is from 5 to 7.5, preferably fromabout 5.7 to about 7.4. The zeolitic materials of the invention havehigh crystallinity as shown by a well-defined X-ray diffraction pattern(without binder or other diluents present) with sharp peaks.Crystallinity may be measured relative to a quartz standard by comparingthe peak areas for the reflection from the 220 plane (d=4.57±0.04 Å) andthe 221 plane (d=3.91±0.02) for the zeolitic material of the inventionwith the peak area for the reflection from the 110 plane (d=2.46±0.02)of the quartz. The ratio of the combined peak areas of the 220 and 221reflections of the zeolitic material to the peak area of the 110reflection of quartz is a measure of the crystallinity of the sample. Toprovide a comparison between different samples and to eliminate cationeffects and peak area determination is preferably carried out on thesame cation form of the zeolite, and in the Examples given herein thepotassium form was chosen.

The exchangeable cation M in general formula I is very preferablypotassium, but it is possible for a part of M to be replaced by othercations such as alkali and alkaline earth metals for example sodium,rubidium or caesium. The ratio M_(2/n) O:Al₂ O₃ is preferably from about0.95 to about 1.15, and generally above 1.

In general formula I x (the mole ratio SiO₂ :Al₂ O₃) is more preferablyfrom about 6 to about 7 and most preferably from about 6.0 to about 6.5.

The aluminosilicate forms of the invention may be hydrated, typicallywith from 0 to about 9 moles of water per mole of Al₂ O₃. When used as acatalyst base, as described hereinafter, the zeolite of the invention ispreferably first calcined to remove water. In normal preparation fromaqueous gels a hydrated form is first prepared and this way bedehydrated by heating.

Scanning electron micrographs (SEM) of the materials of the inventionshow these to have very distinct crystal morphology. As described inmore detail hereinafter, preferred materials of the invention appear asdistinct cylinders in scanning electron micrographs. The terms"cylinder" and "cylindrical" are used herein to describe particleshaving substantially the shape of a cylinder as defined in solidgeometry--that is, a solid bounded by a surface generated by a linemoving parallel to a fixed line so as to cut a fixed plane curve and bytwo parallel planes (bases) which cut the surface. The use of theseterms is not intended to exclude particles having generally cylindricalform but having minor surface irregularities or displaying typicalcrystallographic faults or dislocations. The cylindrical particles ofthe invention are preferably substantially in the form of circularcylinders (circular cross-section) and most preferably substantially inthe form of right circular cylinders (wherein the bases are normal tothe cylinder axis). Particularly preferred cylindrical particles arethose having an aspect ratio (the length of the cylinder surface to thediameter of the cylinder) of at least 0.5. Particles having a loweraspect ratio are also described as discs where they have substantiallyflat basal planes. Cylindrical particles including discs, have beenshown to have excellent properties of extending catalyst life when usedas catalyst bases for aromatization catalysts. This is in contrast toother morphologies, and in particular particles with cylindricalmorphology have been shown better than particles with a clam-like shape.The term "clam" is used to describe particles having two generallyconvex faces joined to give the appearance of a clam shell. Thealuminosilicates of the invention are preferably characterized by atleast about 50%, more preferably about 70% and most preferably about85%, of the crystallites being cylinders. The aspect ratio of thecylindrical crystallites is preferably from about 0.5 to about 1.5.

A further particularly surprising feature of the invention is that largecrystallites wherein the mean diameter of the cylinders is at leastabout 0.1 micron may be prepared. The cylindrical particles preferablyhave a mean diameter of at least about 0.5 micron and this inventionprovides zeolites comprising these large cylindrical crystallites. Thecrystallites are more preferably from about 0.5 to about 4μ, and mostpreferably from about 1.0 to about 3.0μ. It is a further feature of theinvention that there is a relatively narrow particle size distribution,and preferably substantially all the cylindrical particles of zeolitefall within the range of from 0.5 to 4μ. Transmission electrondiffraction indicate these are single crystals rather than agglomerates.It is a further surprising feature of the invention that the zeolitewith cylindrical morphology may be prepared by controlling thecomposition of the reaction mixture within certain limits, dependingupon the aspect ratio required, and that by operating within theselimits it is possible to obtain relatively large cylindrical particlesin a narrow size distribution. Thus, in another aspect the inventionalso provides a process for the preparation of aluminosilicates of theinvention comprising cylindrical crystallites with an aspect ratio of atleast 0.5, in which an alkaline reaction mixture comprising water, asource of silicon and a source of aluminium with a composition fallingwithin the following molar ratios (expressed as oxides):

M₂ O/SiO₂ : 0.22-0.36

H₂ O/M₂ O: 25-90

SiO₂ /Al₂ O₃ : 6-15

(wherein M is a cation of valence n, and preferably potassium or amixture of K+M' in which M' is an alkali metal or alkaline earth metalsuch as sodium, calcium, barium, or rubidium, provided that K₂ O/(M'₂O+K₂ O) is at least 0.7) is heated to a temperature of from at least 75°C. and preferably from about 100° C. to about 250° C., more preferablyfrom about 120° C. to about 225° C., to form the desired cylindricalaluminosilicate.

The ratio of H₂ O/(K₂ O+M'₂ O+SiO₂ +Al₂ O₃) is preferably greater than 6and most preferably greater than 8.

There are four principle components to the reaction mixture or synthesisgel and thus generally:

aluminium

silicon

potassium (optionally with up to 30 mole% replaced by alkali or alkalineearth metal)

water

and the relative proportions of these four components and the chosenreaction conditions are important if the desired cylindricalaluminosilicates of the invention with an aspect ratio of at least 0.5are to be obtained. The proportions of the four components can be showngraphically in a series of four triangular graphs each showing thepercentage composition of three components of the reaction with thecontent the fourth component being excluded from each graph. Asdescribed in more detail hereinafter FIGS. 1 to 4 shows such plots forpreferred reation mixtures giving aluminosilicates of the invention withan aspect of at least 0.5 and, by way of comparison, for reactionmixtures giving conventional Zeolite L and other zeolite and non-zeoliteproducts. These graphs show the composition of reaction mixtures inwhich M is potassium alone, but it is to be understood that as describedhereinbefore up to 30 mole % of potassium may be replaced by anotheralkali or alkaline earth metal and the graphs are to be interpreted withthat in mind.

The four graphs together may be considered as the four faces of athree-dimensional graph in the form of a regular tetrahedron, and thepoints and areas marked thereon represent the projection on those facesof points and volumes within the three-dimensional graph. Thus, while apoint may lie within the area designated as constituting the inventionin one graph, unless it lies within the area of the invention on allfour graphs it does not lie within the volume defined within thethree-dimensional graph as being a preferred reaction mixture of theinvention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a triangular of the content of the reaction mixture (in weightpercentage of oxides excluding alumina) showing the relative propertiesof water, silicon and potassium. To obtain the preferredaluminosilicates of the invention the reaction mixture should desirablylie within the area marked I_(A) in the graph, preferably within thearea marked II_(A) in the graph and most preferably within the areamarked III_(A) in the graph.

FIG. 2 is a triangular graph of the content of the reaction mixture (inweight percent of oxides excluding water) showing the relativeproperties of aluminium, silicon and potassium. To obtain the preferredaluminosilicates of the invention the reaction mixture should desirablylie within the area marked I_(B) in the graph, preferably within thearea II_(B) in the graph and most preferably within the area markedIII_(B) in the graph.

FIG. 3 is a triangular graph of the content of the reaction mixture (inweight percent of oxides excluding silica) showing the relativeproperties of aluminium, water and potassium. To obtain the preferredaluminosilicates of the invention the reaction mixture should desirablylie within the area marked I_(C) in the graph, preferably within thearea II_(C) in the graph and most preferably within the area markedIII_(C) in the graph.

FIG. 4 is a triangular graph of the content of the reaction mixture (inweight percent of oxides excluding potassium oxide) showing the relativeproperties of aluminium, silicon and water. To obtain the preferredaluminosilicates of the invention the reaction mixture should desirablylie within the area marked I_(D) in the graph, preferably within thearea II_(D) in the graph and most preferably within the area markedIII_(D) in the graph.

Very preferably the reaction mixture falls within the areas markedIII_(A), III_(B), III_(C) and III_(D) in the graphs of FIGS. 1, 2, 3 and4, respectively. Such a reaction mixture results in the highestproportion of well-defined crystals particularly when the reactionmixture is heated to the preferred temperature range of about 120° C. toabout 225° C., and most preferably to a temperature of about 150° C.

Zeolite W tends to be formed in some extremes of gel composition. It isadvantageous for the zeolite W content of the product to be minimized.The zeolite W content of the product can be monitored by its X-raydiffraction pattern. A characteristic prominant line in the zeolite WXRD pattern is at 2θ=12.6° (d=7.09 Å), while a prominant line in thezeolite L XRD pattern is at 2θ=22.7° (d=3.91 Å). The relative peakintensities of these peaks can be compared to determine the relativeproportions of the two zeolite types, since these peaks are not obscuredin mixtures of the two zeolites. It is a preferred feature that zeoliteof the invention has an XRD pattern in which the peak height ratio(d=7.09 Å)/(d=3.91 Å) is not greater than 0.2. Very preferably theproduct is substantially free of zeolite W as evidenced by an absence ofthe XRD pattern of a line at a d spacing of 7.90 Å. To achieve this lowlevel of zeolite W contamination the reaction mixture preferablycomprises the reactants in the following molar ratios:

    M.sub.2/n O/SiO.sub.2 =>0.25

    H.sub.2 O/M.sub.2/n O=<65

    SiO.sub.2 /Al.sub.2 O.sub.3 =7.5-10.5

Products with particularly high peak intensities, measured as definedhereinbefore, have been obtained by employing a reaction mixturecomprising the reactants in the following molar ratios:

    M.sub.2/n O/SiO.sub.2 =0.21-0.36

    H.sub.2 O/M.sub.2/n O=28-80

    SiO.sub.2 /Al.sub.2 O.sub.3 =8.5-10.7

Furthermore, the formation of crystallites with cylindrical morphologywith an aspect ratio in excess of 0.5 is found to be favoured byemploying a reaction mixture comprising the reactants in the followingmolar ratios:

    M.sub.2 /nO/SiO.sub.2 =>0.2

    H.sub.2 O/M.sub.2/n O=>40

    SiO.sub.2 /Al.sub.2 O.sub.3 =<22

In particular, an optimum composition for a process in which thereaction mixture is heated to from about 120° C. to about 225° C. hasbeen found to be substantially in the following mole ratios:

    2.62K.sub.2 O:Al.sub.2 O.sub.3 :10SiO.sub.2 :16OH.sub.2 O

and particularly good results have been obtained by heating to about150° C. Investigations of individual variations in the components at acrystallizaton temperature of 150° C. has shown that good yields ofcylindrical aluminosilicate are obtained if the water content in theoptimum composition is reduced to 120 moles in the above ratio, but thatfurther reduction in the water content still results in the formation ofa good yield of Zeolite L but increasingly in the form of clam-shapedparticles. In particular, at 80 moles water a high yield of clams isobtained. Thus, at the mole ratio of

    H.sub.2 O/K.sub.2 O+Na.sub.2 O+Al.sub.2 O.sub.3 +SiO.sub.2 less than 6

specified in GB 1 202 511 the aluminosilicates of the invention are notobtained. If the water content in the optimum ratio is increased thealuminosilicate of the invention is still obtained at 240 moles water,but at 320 moles water a significant amount of contaminating Zeolite Wphase is obtained.

Similarly it is possible to obtain the aluminosilicate of the inventionif the silica content in the optimum composition is varied between about8 and about 12 moles, but at higher levels of silica there is anincreasing proportion of amorphous material and at lower levels ofsilica Zeolite W again is produced in larger amounts.

The reaction mixture is particularly sensitive to the content of K₂ O(or of M₂ O as defined hereinbefore) and variations in the K₂ O contentin the optimum composition beyond the range of about 0.24 to about 0.30moles gave at higher levels of K₂ O an increasing proportion ofclam-shaped Zeolite L particles and at lower levels of K₂ O a lesscrystalline product.

The variation of alumina content from that specified in the optimumcomposition set out above shows that variation of alumina from about 0.6to about 1.3 moles was possible with the aluminosilicate of theinvention still being a product. Low levels of alumina of the order of0.5 moles resulted in an amorphous product.

Thus, the preferred aluminosilicates of the invention may be obtainedwithin the following preferred ranges:

K₂ O/SiO₂ : 0.24-0.30

H₂ O/K₂ O: 35-65

SiO₂ /Al₂ O₃ : 8-12

In addition to varying the proportions of the reactants in the reactionmixture it is possible to vary the reaction conditions and in particularthe crystallization temperature. By using different temperatures it ispossible to deviate further from the optimum composition defined abovefor a crystallization temperature of 150° C. and yet still obtain thedesired product. In general, within the broad reactant ratios definedfor the process of the invention a higher crystallization temperatureenables the silicon content to be lowered and/or the water content to belowered and/or the potassium content (and thus the alkalinity) to beraised. By contrast operating at lower temperatures tends to decreasethe nucleation rate which can be countered by lowering the alkalinityand/or by increasing the water content and/or by introducing seeds ofperformed zeolite L. When operating in larger scale syntheses it hasbeen found advantageous to minimise the temperature difference at anytime within the crystallization gel, preferably to not more than 15° C.,more preferably not more than 10° C. This may be done by a slow heatingof the crystallization vessel or by limiting the maximum walltemperature of the heat-up.

A disc-shaped material of the invention, having an aspect ratio of lessthan 0.5, which also shows an improvement over conventionally preparedzeolite L when used as a catalyst base in aromatization, may be preparedfrom somewhat different synthesis gels. An optimum synthesis gelcomposition for forming a disc-shaped product at a temperature of fromabout 120° C. to about 225° C., and particularly about 150° C., hassubstantially the following mole ratios:

    16K.sub.2 O:Al.sub.2 O.sub.3 :4OSiO.sub.2 :64OH.sub.2 O

and similar consideration apply in varying the composition ortemperature as discussed hereinbefore. Preferred ranges of the ratio ofthe components for the production of disc-shaped products are asfollows:

    M.sub.2/n O/SiO.sub.2 =0.23-0.36

    H.sub.2 O/M.sub.2/n O=30-80

    SiO.sub.2 /Al.sub.2 O.sub.3 =20-60

In the synthesis of all zeolitic materials of the invention, the sourceof silicon for the reaction mixture is generally silica, and this isusually most conveniently in the form of a colloidal suspension ofsilica such as Ludox HS 40 available from E. I. Dupont de Nemours andCo. Colloidal silicon sols are preferred since they result in lesscontaminating phases. However other forms such as silicates may be used.

The source of aluminium may be an alumina introduced into the reactionmedium as, for example, Al₂ O₃.3H₂ O, previously dissolved in alkali.However, it is also possible to introduce aluminium in the form of themetal, which is dissolved in alkali.

The aluminosilicates of the invention are preferably obtained fromreaction mixtures containing potassium. This potassium is preferablyintroduced as potassium hydroxide. The reaction mixture may containsmall quantities of other metal cations and salt forming anions asalready described, but it has been found that there is an increasingtendency for other alumino-silicates to be found as the content of otherions is increased, resulting in less pure forms of the alumino-silicateof the invention. For example, sodium and rhubidium ions favour erioniteformation, caesium ions favour pollucite formation. Thus it is highlypreferred for potassium hydroxide to be the source of potassium and thesource of alkalinity, and the purest products were obtained when otherpotassium salts were excluded.

The product of the processes described above is predominantly apotassium form of the aluminosilicate-that is, aluminosilicate where Min general formula I is K. By ion exchange of the product in the mannerconventional to zeolite chemistry other cations such as Na or H can beintroduced for M.

Within the ranges specified hereinbefore for the composition of thereaction mixture it is possible to choose ratios of oxides andalkalinity to given particular forms of the aluminosilicate product.However, although the SiO₂ /Al₂ O₃ ratio in the reaction mixture mayvary over a wide range the SiO₂ /Al₂ O₃ ratio in the product preferablylies in a relatively narrow range of 5.7 to 7.4. The higher the SiO₂/Al₂ O₃ ratio in the reaction mixture, the higher the ratio in theproduct. Also, decreasing alkalinity (OH⁻ /SiO₂) tends to increase theSiO₂ /Al₂ O₃ ratio in the formed product. Dilution of the reactionmixture with water and thus increasing the H₂ O/K₂ O ratio also tends toincrease the SiO₂ /Al₂ O₃ ratio in the product. Other cations such astetramethylammonium and the presence of other potassium salts can beused to raise the SiO₂ /Al₂ O₃ ratio, but as described hereinbefore thismay also result in the formation of other zeolite forms.

Particle size is also affected by the composition of the reactionmixture. Generally the particles formed are in the range of from about0.5 to about 4.0μ, but within that range larger particle sizes arefavoured by each of lower alkalinity, higher dilution and highertemperatures.

Crystallization is related to the crystallization temperature. Thecrystallization is preferably carried out in the region of 150° C. andat this temperature the crystallization time may be from about 24 to 96hours, typically from 48 to 72 hours. Lower temperatures may requiremuch longer times to achieve good yield of the desired product, whereastimes of less than 24 hours are possible when higher temperatures areused. A time of 8 to 15 hours is typical for a temperature of greaterthan 200° C.

The crystallization is generally carried out in a sealed autoclave andthus at autogenous pressure. It is generally inconvenient, althoughpossible to employ higher pressures. Lower pressure will require longercrystallization times.

Following the preparation as described above the aluminosilicate may beseparated, washed and dried in the normal manner.

The products of the processes of the invention described hereinbeforeare preferably substantially free from contaminant crystalline andamorphous materials. However, in employing these products in catalyticapplications it may be desired to combine them with additionalcrystalline or amorphous materials and this invention extends to suchcombinations.

We have found that the aluminosilicates of the invention are excellentcatalyst bases and may be used in a wide variety of catalytic reaction.The particular morphology of the crystals appears to result in aparticular stable base for catalytically active metals with a surprisingresistance to metal catalyst deactivation. In addition, thealuminosilicates of the invention have displayed low acidity which makesthem especially suited to catalytic applications where a low acid sitestrength is advantageous such as aromatization.

The catalytically-active metal(s) may be, for example, a Group VIIImetal such as platinum, tin, or germanium as described in U.S. Pat. No.4,104,320, or a combination of platinum and rhenium as described in GB 2004 764 or BE 888365. In the latter case the catalyst may forappropriate circumstances also incorporate halogen as described in U.S.Pat. No. 4,165,276, silver as described in U.S. Pat. No. 4,295,959 andU.S. Pat. No. 4,206,040, cadmium as described in U.S. Pat. No. 4,295,960and U.S. Pat. No. 4,231,897 or sulphur as described in GB 1 600 927.

We have found a particularly advantageous catalyst composition toincorporate from about 0.1 to about 6.0 weight %, preferably from about0.1 to about 1.5 weight % platinum or palladium, since this givesexcellent results in aromatization. From about 0.4 to about 1.2 wt %platinum is particularly preferred, especially in conjunction with thepotassium form of the aluminosilicate. The invention extends tocatalysts comprising the zeolitic material and a catalytically-activemetal.

It may also be useful to incorporate into the catalyst of the inventionone or more materials substantially inert under the conditions in whichthe catalyst is to be employed to act as a binder. Such binders may alsoact to improve the resistance of the catalyst to temperature, pressureand attrition.

The aluminosilicates of the invention may be used in a process for theconversion of a hydrocarbon feed in which the feed is contacted with acatalyst as described above under appropriate conditions to bring aboutthe desired conversion. They may for example be useful in reactionsinvolving aromatization and/or dehydrocyclization and/or isomerizationand/or dehydrogenation reaction. They are particularly useful in aprocess for the dehydrocyclization and/or isomerization of acyclichydrocarbons in which the hydrocarbons are contacted at a temperature offrom about 430° C. to about 550° C. with a catalyst comprising analuminosilicate of the invention having at least 90% of the exchangeablecations M as alkali metal ions and incorporating at least one Group VIIImetal having dehydrogenating activity, so as to convert at least part ofthe acyclic hydrocarbons into aromatic hydrocarbons.

The process is preferably otherwise carried out in the manner describedin U.S. Pat. No. 4,104,320, BE 888365 or EP 40119.

It has been found that use of the aluminosilicates of the invention inthis way enables greatly improved catalyst lifetimes to be achieved ascompared to the lifetime obtained with a conventionally preparedzeolite.

The invention will now be described in more detail, though only by wayof limitation, in the following Examples and Evaluations, with referenceto the accompanying drawings, in which:

FIGS. 1 to 4 are, as described hereinbefore, triangular graphs showingthe preferred proportions of components of the synthesis gel. On thesegraphs the reaction mixtures used in the Examples in the production ofaluminosilicates of the invention are shown as crosses identified by thenumber of Example, and those reaction mixtures used in the ComparativeExamples are shown as solid circles identified by the letter of theComparative Example; and

FIG. 5 is a graph showing the performance of catalysts of the inventionin aromatization against catalysts based on conventional zeolites.

For convenience, the aluminosilicates of the invention will be referredto as "zeolite EL" or simply "EL".

EXAMPLE 1: PREPARATION OF ZEOLITE EL

A synthesis gel was prepared having the following composition expressedin moles of pure oxide:

    2.62K.sub.2 O:Al.sub.2 O.sub.3 :10SiO.sub.2 :16OH.sub.2 O

This gel was prepared as follows:

23.40 g of aluminium hydroxide was dissolved by boiling in an aqueoussolution of 51.23 g of potassium hydroxide pellets (86% pure KOH) in100.2 g to form solution A. After dissolution any water loss wascorrected. A separate solution, solution B, was prepared by diluting a225 g of colloidal silica (Ludox HS40) with 195.0 g of water.

Solutions A and B were mixed for two minutes to form 224 g of gel, andjust before the gel became fully stiff it was transferred toTeflon-lined autoclaves, preheated to 150° C. and held at thattemperature for 72 hours to bring about crystallization.

The formed Zeolite EL was highly crystalline with a typical Zeolite LX-ray diffraction (XRD) pattern. Scanning electron micrographs (SEM)show the product to be formed solely of well-defined cylindricalcrystals having a particle size of 2 to 2.5 microns. The SiO₂ :Al₂ O₃ratio in the product was 6.3. K₂ O:Al₂ O₃ was measured as 0.99.

COMPARATIVE EXAMPLE A REPETITION OF U.S. PAT. NO. 3,867,512. EXAMPLE 9

A synthesis gel was prepared using the procedure of Example 9 of U.S.Pat. No. 3,867,512 which is judged to be the disclosure in that priorart document which provides the most relevant comparison with theinvention, although presented in U.S. Pat. No. 3,867,512 as acomparative example. 2.92 g of aluminium hydroxide were dissolved in asolution of 19.52 g of potassium hydroxide in 24.0 g water to formsolution A. 56.5 g Ludox HS40 were dissolved in 101.0 g water to formsolution B. Solutions A and B were mixed for two minutes to formsynthesis gel. Crystallization was carried out at 116° C. for 68 hours,and the product was separated as in Example 1. The combination was:

    8.0K.sub.2 O:20SiO.sub.2 :Al.sub.2 O.sub.3 :72OH.sub.2 O

and thus very dilute, and more alkaline than required by the presentinvention. The product was Zeolite L but contained no cylindricalcrystallites which are the characteristic product of the presentinvention.

COMPARATIVE EXAMPLE B--REPETITION OF NISHIMURA

The synthesis procedure described in Y. Nishimura, Nippon Kagaku Zasshi91, 11, 1970, pp1046-9 was repeated to prepare a gel composition:

    8.0K.sub.2 O:Al.sub.2 O.sub.3 :10SiO.sub.2 :500H.sub.2 O

This was crystallized in an autoclave at 100° C. for 65 hours.

The Japan disclosure is of gels which are more dilute and of highalkalinity than required for the present invention. The product of thisComparative Example was essentially Zeolite W, not Zeolite L and therewas no trace of Zeolite EL of this invention.

COMPARATIVE EXAMPLE C REPETITION OF DT 1813099 EXAMPLE 6

A synthesis gel was prepared having substantially the compositiondescribed in Example 6 of DT 1813099 (equivalent to GB 1 202 511):

    2.75K.sub.2 O:Al.sub.2 O.sub.3 :8.7SiO.sub.2 :100H.sub.2 O

7.37 g of aluminium hydroxide were dissolved in an aqueous solution of16.98 gms of potassium hydroxide (86% pure KOH) in 30.9 gms water toSolution A. 25.04 g of silica as Aerosil 200 were mixed with 55.4 gwater for 5 minutes to form Solution B. Solutions A and B were mixed for1 minute and the formed putty-like gel was heated in an autoclave at140° C. for 46.5 hours.

The product was separated and dried as in Example 1. XRD and SEM showedthe product to be a mixture of Zeolite W with Zeolite L. No cylindricalcrystallites characteristic of the invention were observed. Theprocedure of DT 1813099 used drier gels than the present invention andsomewhat higher alkalinity, so that effectively the gel alkalinity wassignificantly higher.

EXAMPLES 2 AND 3 AND COMPARATIVE EXAMPLE H VARIATION OF ALUMINIUMCONTENT

The general procedure of Example 1 was repeated with different amountsof aluminium present in the gel. The gels employed are detailed in Table1 below, together with an indication of the products obtained.

Example 3 (2.58K₂ O:0.67Al₂ O₃ :10SiO₂ :160H₂ O) and Example 2 (2.62K₂O:1.25Al₂ O₃ :10SiO₂ :160H₂ O) yielded Zeolite EL of the invention andExample 3 gave a particularly high yield (20%--measured as zeoliteproduct as a percentage of the initial gel weight). Comparative ExampleH (2.58K₂ O:0.5Al₂ O₃ :10SiO₂ :160H₂ O) gave a large amorphous product.

EXAMPLES 4 AND 5 AND COMPARATIVE EXAMPLES D AND E VARIATION OF WATERCONTENT

The procedure of Example 1 was repeated for further syntheses usingvarious amounts of water. The gel composition and results are given inTable 1 below.

Example 4 (2.62K₂ O:Al₂ O₃ :10SiO₂ :120H₂ O) gave good yields ofcylindrical Zeolite EL, but as the water content is further reducedthere is a tendency to form clam-shaped particles. Comparative Example D(2.62K₂ O:Al₂ O₃ :10SiO₂ :80H₂ O) resulted in a high proportion of clamZeolite L.

Example 5 shows that increasing the water content to 240 moles H₂ Ostill resulted in Zeolite EL, but as water is increased there is anincreasing product of Zeolite W. At 320 moles H₂ O in ComparativeExample E Zeolite W predominates.

EXAMPLES 6-8 AND COMPARATIVE EXAMPLES F AND G VARIATION IN SILICONCONTENT

A similar investigation of the variation of silicon content of thesynthesis gel of Example 1 was carried out as shown in Table 1.Increasing silicon content resulted in an increasing amount ofcontaiminating phases of Zeolite W and amorphous material, but Example 6with 12 moles SiO₂ gave a satisfactory Zeolite EL product. ComparativeExample F using 15 moles SiO₂ gave a largely amorphous product.

The silicon content was reduced in Example 8 to 8 moles SiO₂ withsatisfactory Zeolite EL product, but further reduction to 7 moles SiO₂in Comparative Example G gave a product containing Zeolite W and ZeoliteL.

EXAMPLES 9, 10 AND 11 AND COMPARATIVE EXAMPLES J AND K VARIATION OFPOTASSIUM CONTENT

As shown in Table 1, the variation of the amount of potassium in thecase where M=K was also investigated. Variation of potassium contentfrom 2.41 moles K₂ O (Example 10) to 2.75 moles K₂ O (Example 9) gaveZeolite EL. Example 11 gave Zeolite L with a morphology intermediate theclam shape and the cylinder shape.

A low potassium content of 2.15 moles K₂ O (Comp. Ex. K) gave a productwith low crystallinity. A high potassium content of 3.4 moles K₂ O(Comp. Ex. J) gave a clam-shaped product.

                                      TABLE 1                                     __________________________________________________________________________           GEL COMPOSITION                                                               (moles)      (wt %)                                                    EXAMPLE                                                                              K.sub.2 O                                                                        Al.sub.2 O.sub.3                                                                  SiO.sub.2                                                                        H.sub.2 O                                                                        K.sub.2 O                                                                        Al.sub.2 O.sub.3                                                                  SiO.sub.2                                                                        H.sub.2 O                                                                        PRODUCT*                                     __________________________________________________________________________    1      2.62                                                                             1   10 160                                                                              6.4                                                                              2.7 15.7                                                                             74.6                                                                             cylindrical zeolite EL                       2      2.62                                                                             1.25                                                                              10 160                                                                              6.4                                                                              3.4 15.6                                                                             74.6                                                                             zeolite L                                    3      2.58                                                                             0.67                                                                              10 160                                                                              6.4                                                                              1.8 15.8                                                                             76.0                                                                             cylindrical zeolite EL +                     H      2.58                                                                             0.50                                                                              10 160                                                                              6.4                                                                              1.4 15.9                                                                             76.3                                                                             amorphous                                    4      2.62                                                                             1   10 120                                                                              7.9                                                                              3.3 19.3                                                                             69.5                                                                             cylindrical zeolite EL                       5      2.62                                                                             1   10 240                                                                              4.7                                                                              1.9 11.4                                                                             82.0                                                                             cylindrical zeolite EL + (W)                 D      2.62                                                                             1   10  80                                                                              10.3                                                                             4.3 25.1                                                                             60.3                                                                             clam-shaped zeolite L                        E      2.62                                                                             1   10 360                                                                              3.7                                                                              1.5  8.9                                                                             85.9                                                                             zeolite W + (zeolite L)                      6      2.62                                                                             1   12 160                                                                              6.2                                                                              2.6 18.2                                                                             72.9                                                                             zeolite EL + (W + amorphous)                 7      2.62                                                                             1    9 160                                                                              6.5                                                                              2.7 14.3                                                                             76.4                                                                             cylindrical zeolite EL                       8      2.58                                                                             1    8 160                                                                              6.5                                                                              2.8 13.0                                                                             77.7                                                                             cylindrical zeolite EL (+ W)                 F      2.62                                                                             1   15 160                                                                              6.0                                                                              2.5 21.8                                                                             69.8                                                                             amorphous                                    G      2.62                                                                             1    7 160                                                                              6.8                                                                              2.8 11.5                                                                             78.9                                                                             zeolite W + (zeolite L)                      9      2.75                                                                             1   10 160                                                                              6.7                                                                              2.7 15.6                                                                             75.0                                                                             cylindrical zeolite EL                       10     2.41                                                                             1   10 160                                                                              5.9                                                                              2.7 15.8                                                                             75.6                                                                             cylindrical zeolite EL                       11     3.01                                                                             1   10 160                                                                              7.3                                                                              2.6 15.5                                                                             74.5                                                                             clam/cylinder zeolite EL                     K      2.15                                                                             1   10 160                                                                              5.3                                                                              2.7 15.9                                                                             76.1                                                                             low crystallinity product                    J      3.4                                                                              1   10 160                                                                              8.2                                                                              2.6 15.4                                                                             73.8                                                                             clam-shaped zeolite L                        __________________________________________________________________________     *"+" indicates that small amounts of other phases were present. Where         other phases were indentified these are shown in parenthesis.            

FIGS. 1 to 4 plot the relative proportions of the components of the gelcomposition and the preferred proportions for these components in theprocess of the invention. The Examples of the invention are marked asnumbered crosses and the Comparative Examples are shown as lettereddots. This clearly demonstrates that the areas of preferred gelcomposition marked on the Figures correspond to gels yielding zeoliteEL.

Various additional tests have been carried out on substitution ofpotassium by other metals such as sodium. Since this introduces afurther variable it is not possible to show these results in FIGS. 1 to4.

EXAMPLES 12-14 REPLACEMENT OF POTASSIUM

Example 1 was repeated in a generally similar manner but a part of thepotassium hydroxide used in preparing Solution A was replaced by sodiumhydroxide. Replacement of 10, 20 and 30 mole % was effected and productwere obtained and analysed by XRD and SEM. The results are set out inTable 2 below:

                  TABLE 2                                                         ______________________________________                                        Ex-                                                                           am-  Gel Composition (moles)                                                  ple  K.sub.2 O                                                                            Na.sub.2 O                                                                            Al.sub.2 O.sub.3                                                                    SiO.sub.2                                                                          H.sub.2 O                                                                          Product                                   ______________________________________                                        12   2.36   0.26    1     10   160  cylindrical zeolite EL                    13   2.10   0.52    1     10   160  cylindrical zeolite EL                    14   1.83   0.78    1     10   160  cylindrical zeolite                       ______________________________________                                                                            EL                                    

COMPARATIVE EXAMPLE L REPETITION OF U.S. PAT. NO. 3,216,789 EXAMPLE 4

The procedure of Example 4 of U.S. Pat. No. 3,216,789 was repeated toprepare a synthesis gel of molar composition (based on actual puritiesof reactants):

    (2.7K.sub.2 O+0.7Na.sub.2 O):Al.sub.2 O.sub.3 :10SiO.sub.2 :135H.sub.2 O

This was then crystallized at 150° C. for 45 hours and worked up asdescribed in U.S. Pat. No. 3,216,789. The product was a crystallinezeolite L but the crystallites were clam-shaped and there was no traceof cylindrical Zeolite EL of the invention. This result is consistentwith the trend noted in increasing alkalinity from Example 9 toComparative Example J.

COMPARATIVE EXAMPLE M REPETITION OF TSITSISHVILLI

The synthesis procedure described in Tsitsishvilli et al, DokladyAkademii Nauk SSSR, Vol 243, No 2, pp438-440 (1973) was repeated toprepare a gel with a molar composition:

    5.99K.sub.2 O:12.00Na.sub.2 O:Al.sub.2 O.sub.3 :25SiO.sub.2 360H.sub.2 O

and containing tributylamine at a rate of 37 ml tributylamine in 132 gof gel. This was crystallized at 100° C. for 45 hours.

This synthesis, which differs from the invention in using highalkalinity, high sodium content and an organic component, gave a productthat was largely Zeolite W with a second unidentified phase. No ZeoliteEL was identified in the product.

EXAMPLE 15: ZEOLITE EL PREPARATION USING ALUMINIUM AS METAL

A synthesis gel of 133 g was prepared having a composition (measured asmoles of pure oxide per mole of aluminium measured as Al₂ O₃) 2.60 molesK₂ O, 10 moles SiO₂ and 160 moles water. The following method wasemployed:

Aluminium pellets were dissolved in an aqueous solution of potassiumhydroxide (86% pure) by heating. After complete dissolution extra waterwas added to correct for weight losses. Finally the silica source, adiluted Ludox HS 40 solution, was added. The mixture containing allcomponents was mixed for 4 minutes in a high sheer mixer. The resultingaluminosilicate gel was charged to a clean Teflon-lined autoclave(within a few minutes a very viscous gel is obtained). The filledautoclave was put in an already heated oven (150° C.) and maintained atthat temperature for 48 hours to allow zeolite crystallization.

The solid product was separated by centrifuging, washed with cold water(4 times) and dried at 150° C. for 4 hours.

The formed zeolite EL was in the form of large (1.5-2.5u) crystals witha cylindrical shape. The SiO₂ /Al₂ O₃ ratio in the product was 6.3.

EXAMPLE 15 AND COMPARATIVE EXAMPLES O TO W

The procedure of Example 15 was repeated with different synthesis gelsto form viscous Zeolite L samples. The synthesis gels and the productsobtained are summarized in Table 3 below. Example 16 formed adisc-shaped zeolite EL product with good crystallinity. In theComparative Examples the Zeolite EL product of the invention was notobtained.

                                      TABLE 3                                     __________________________________________________________________________                  GEL COMPOSITION (moles)                                                                             PRODUCT                                   EXAMPLE                                                                              GEL Wt (g)                                                                           K.sub.2 O                                                                         SiO.sub.2                                                                         Al.sub.2 O.sub.3                                                                  H.sub.2 O                                                                         Zeolite                                                                             Shape                                                                             Size (u)                                                                           SiO.sub.2 /Al.sub.2 O.sub.3      __________________________________________________________________________    16     116    14.1                                                                              40  1   640 EL    Disc                                                                              0.5-1                                                                              7.4                              O      270    3.5 10  1   160 L     Clam                                                                              1.5-2.6                                                                            5.6                              P      230    3.5 20  1   640 Amorphous                                                                           --  --                                    Q      140    3.5 20  1   160 Amorphous                                                                           --  --                                    R      114.sup.(a)                                                                          3.5 10  1   160 L     Sphere                                                                            0.3-0.5                                                                            5.6                              S      134.sup.(b)                                                                          3.5 10  1   160 L     Clam                                                                              1.5-2.5                                                                            6.1                              T      134.sup.(c)                                                                          3.5 10  1   160 L     Clam                                                                              1.5-2.5                                                                            5.8                              U      138    4.4 10  1   160 L     Sphere                                                                            0.3-0.5                                                                            5.0                              V      135    3.5 10  1   160 L     Clam                                                                                1-2.5                                                                            5.4                              W       83    3.5 10  1    84 L     Sphere                                                                            0.1-0.2                                                                            5.4                              __________________________________________________________________________     .sup.(a) silicon source = hydrated silicic acid SiO.sub.2.nH.sub.2 O          .sup.(b) aluminium source = 50% Al 50% Al.sub.2 O.sub.3.3H.sub.2 O            .sup.(c) aluminium source = 25% Al 75% Al.sub.2 O.sub.3.3H.sub.2 O       

COMPARATIVE EXAMPLES X: EFFECT OF ANIONS

Example 15 was repeated except that an additional mole of potassium(measured as moles K₂ O/mole Al₂ O₃) was introduced as a potassium salt.This gave the gel the following composition (in terms of moles ofoxides):

    3.5K.sub.2 O:Al.sub.2 O.sub.3 :10SiO.sub.2 :160H.sub.2 O

The products of the crystallization showed mixed crystallite types whichindicated that mixtures of zeolite types were formed. Zeolite W wasidentified by its X-ray diffraction pattern. The additives alsoincreased the SiO₂ /Al₂ O₃ ratio in the product. The results are givenin Table 4 which follows:

                  TABLE 4                                                         ______________________________________                                                         Product                                                                       Zeolite                 SiO.sub.2 /                          Comp Ex                                                                              Additive  type     Shape   Size (u)                                                                             Al.sub.2 O.sub.3                     ______________________________________                                        Xa     KBr       L        clam & disc                                                                           2.5-3  6.8                                  Xb     KCL       L and W  clam    3-4    7.2                                  Xc     K.sub.2 CO.sub.3                                                                        L and W  clam &  2-3    6.5                                                            irregular                                           Xd     K.sub.2 SO.sub.4                                                                        L and W  disc &    2-2.5                                                                              6.8                                                            cylinder                                            Xe     K toluene L and W  irregular                                                                             0.5    6.9                                         sulphonate                                                             ______________________________________                                    

COMPARATIVE EXAMPLES Y: REPEAT OF GB 1 393 365

Example 10 of GB 1 393 365 describes a synthesis mixture with thecomposition:

    2.7M.sub.2 O:Al.sub.2 O.sub.3 :8.75SiO.sub.2 :83.7H.sub.2 O

wherein K₂ O/M₂ O (i.e. K₂ O+Na₂ O)=0.8 for the preparation of zeoliteAG-1. GB 1 393 365 specifies a water glass starting material for thissynthesis with the composition:

    Na.sub.2 O:4.0SiO.sub.2 :42.6H.sub.2 O.

However, the use of such a silicon source makes it impossible to complywith the other requirement of GB 1 393 365 that the water glass shouldbe the only or major source of silicon.

A synthesis mixture of the specified composition was prepared usingpotassium aluminate and Ludox Hs-40 as the raw materials. A similarsynthesis (not described in GB 1 393 365) was also performed using amixture containing no sodium. The results are given in Table 5 below.The products had poor crystallinity, and showed clam morphology.

                  TABLE 5                                                         ______________________________________                                                       Crystal-   Product                                             Gel composition                                                                              lization   characteristics                                     mole/mole Al.sub.2 O.sub.3                                                                   Temp    time             size                                  Na.sub.2 O                                                                          K.sub.2 O                                                                            SiO.sub.2                                                                            H.sub.2 O                                                                          °C.                                                                          hrs  zeolite                                                                             shape  (um)                         ______________________________________                                        --    2.70   8.75   83.7 135   25   L     clam  0.5-1                         0.54  2.16   8.75   83.7 135   25   L     clam  0.5-1                         ______________________________________                                    

EXAMPLE 17: SCALED-UP SYNTHESIS

The synthesis of Example 1 was repeated in a 2 liter autoclave with adiameter of 10.2 cms using amounts of reactants increased to give atotal synthesis gel weight of 1709 grams. A heating-up period of 9 hourswas employed to bring the gel to the crystallization temperature of 150°C. so that a maximum temperature difference of 10° C. was obtained inthe gel. 260 grams of a highly crystalline zeolite EL product wasobtained, with the crystals having a particle size of 1 to 1.5u andsubstantially all of the particles having a cylindrical morphology.

X-RAY DIFFRACTION

X-ray diffraction patterns were obtained for the product of Example 17and Comparative Example 0, and these were compared with the patterns forEC-19, a zeolite L sample obtained from Union Carbide Corporation, andthe patterns for quartz, a quartz standard called Arkansas Stoneobtained from Deane Smith at the University of Pennsylvania (providedwith all Phillips Instruments).

The samples for the X-ray diffraction measurements were prepared by twotechniques, to give a hydrated and a dried sample.

HYDRATED SAMPLE PREPARATION

The sample as synthesized was loaded into a diffractometer cell withoutfirst washing. It was then hydrated by being placed for at least 16hours in a closed vessel over saturated calcium chloride. The cell wastaken from the vessel and immediately placed in the diffractometer.

DRY SAMPLE PREPARATION

The sample after synthesis was washed 5-6 times with cold demiwater andthe washings decanted by centrifuging. The sample was dried for 16 hoursat 150° C. in air, and then homogenized by hand using a mortar andpestle, and loaded into the diffractometer cell.

DIFFRACTOMETER

The XRD measurements were taken on a Phillips APD 3600 diffractometerusing CuKα radiation operating as follows:

X-ray tube energy: 40 mA, 45 kV

Measuring time: 0.6 sec

Scan speed: 1° 20/min

Scanning range: 4°-100°

Step width: 0.01°

The diffractometer incorporates a theta compensating slit and isintegral with a Data General Nova 4X computer using Phillips Software toprocess the data.

PROCEDURE

The XRD patterns were measured in the following sequence:

Quartz

Hydrated samples

Quartz

Dry samples

Quartz

The peak heights and peak areas for quartz used in the followingcalculations were the average of the 3 quartz samples. The XRD patternsfor d values above 2 Å are given in Tables 6 and 7.

In addition, the peak heights of the eight peaks identified in the tablewere summed and divided by the sum of the peak height for the peaks inthe quartz pattern at d values of:

4.26±0.04

3.35±0.04

2.46±0.02

The ratio gives a measure of the relative peak height of the samples. Itwill be noted that the peak heights of the Example 17 product aregreater than the peak heights of EC-19 or the Comparative Example 0product.

CRYSTALLINITY

The XRD data was analysed to determine the ratio of the peak areas forthe reflection from the plane 220 (d=4.57±0.04 Å) and 221 plane(d=3.91±0.02 Å) of the zeolite to the peak area for the reflection fromthe 110 plane (d=2.46±0.02 Å) of the quartz. The peaks were chosen asbeing in areas where there was no overlap with other peaks and beingrelatively insensitive to hydration effects.

For each peak the integrated area was determined and expressed as apercentage of the quartz peak. The sum of these percentages for the twopeaks are given in Tables 6 and 7. A straight line background wascalculated in determining these peak areas by a least-squares fit oflinear equation through portions of the scan on either side of the peakin question. The area A then calculated as: ##EQU1## where I_(i) themeasured intensity and B_(i) the calculated background for each point ibetween T₁ and T₂ which are the initial and final 20 integration values.

The results show the product of Example 17 to have good crystallinity.

XRD PATTERNS

It is noted that the dry and hydrated samples of the product of Example17 showed an absence of reflections at d spacings of 6.28±0.05 Å

EVALUATION: AROMATIZATION

The performance of certain of the Zeolite EL samples of the Examples asa catalyst base in aromatization was compared to products of theComparative Examples, and a zeolite L, designated EC19, obtained fromUnion Carbide Corporation, referred to a "Control". In each case acatalyst was prepared by impregnating the base with 0.6 wt% platinum.

The zeolite sample under test (typically about 25 g) was slurried in 700ml of distilled water in a 5 liter flask. The appropriate amount oftetraammino-platinum dichloride to give impregnation at a rate of 0.6wt% platinum was dissolved in 300 ml of distilled water. The platinumsalt solution was then added to the sample slurry over an 6 hour period.The mixture was stirred for 24 hours after platinum salt addition, thenthe impregnated sample was dried at 110° C.

The sample was then pelletized, crushed to 14-20 mesh (U.S. sieve size)and loaded into a vertical tubular reactor and air (substantiallywater-free) was passed over the catalyst at a rate of 25 ml/min of airper gram of sample. The catalyst was heated to 480° C. in four hours andheld at 480° C. for three hours. The sample was then reduced by passinghydrogen over it at 207 kPa and a rate of 75 ml/min per gram of sample,while the catalyst was heated to 527° C. in 3 hours, held at 527° C. forten minutes and then cooled to the desired reaction temperature.

The aromatization test was carried out at a temperature of 510° C. and690 KPa (100 psig) pressure with a C₆ mixed feed comprising:

    ______________________________________                                        Component         wt %                                                        ______________________________________                                        iso-C.sub.6       30                                                          (3-methyl-pentane)                                                            n-C.sub.6         60                                                          methyl cyclopentane                                                                             10                                                          ______________________________________                                    

at a space velocity of 2.5 w/w hr⁻¹ and in the presence of hydrogen, theH₂ : hydrocarbons ratio being 6.

The results are shown graphically in FIG. 5, which shows the benzeneyield (weight %) as a function of time. The catalyst using thecylindrical aluminosilicate of Example 15 as its catalyst base show aremarkable improved activity life time over extended periods of time,much greater than that achieved with catalysts using the clam-shapedzeolite L of Comparative Examples Xb and O or using the conventionalzeolite L of the Control. The disc-shaped aluminosilicate of theinvention also shows a significant advantage over the Control.

It is a further feature of the aluminosilicate of the invention that inthe aromatization evaluation described herein, a catalyst comprising 0.6wt% platinum of the aluminosilicate has a benzene yield of 45 wt% afterat least 150 hours, and preferably after 200 hours.

In a repeat of this test the product of Example 17 gave benzene yieldsin excess of 40% for a period of 430 hours.

                  TABLE 6                                                         ______________________________________                                        XRD patterns of hydrated samples                                              EC-19      Comparative Example O                                                                          Example 17                                              Relative           Relative       Relative                              d(Å)                                                                            Intensity                                                                              d(Å)  Intensity                                                                              d(Å)                                                                            Intensity                             ______________________________________                                        16.0  65       15.9      58       15.7  61                                    7.95   4       7.93       4       7.96   4                                    7.52  21       7.52      21       7.51  18                                    6.02  33       6.01      28       6.01  29                                    5.82  15       5.82      12       5.81  13                                    *4.59 61       *4.60     52       *4.59 53                                    4.42  22       4.42      18       4.41  19                                    4.34  20       4.34      13       4.33  18                                    *3.92 87       *3.92     91       *3.92 75                                    3.81   7       3.81       9       3.81   8                                    *3.66 44       *3.66     47       *3.66 44                                    *3.48 63       *3.48     71       *3.48 66                                    3.40   4       3.40       5       3.40   6                                    *3.29 44       *3.29     41       *3.28 43                                    *3.19 100      *3.19     97       *3.18 100                                   *3.07 74       *3.07     78       *3.07 73                                    3.01  12       3.01      12       3.01  11                                    *2.91 89       *2.91     100      *2.91 85                                    2.84   4       2.86       7       2.86   6                                    2.80  12       2.84       8       2.84   8                                    2.73   2       2.79      11       2.79  13                                    2.68  24       2.68      23       2.72   3                                    2.66  60       2.66      57       2.67  20                                    2.62   5       2.62      31       2.65  47                                    2.51  16       2.55       3       2.62  29                                    2.48  20       2.51      19       2.55   5                                    2.43  20       2.47      19       2.50  14                                    2.38   3       2.43      19       2.47  21                                    2.35   3       2.42      14       2.43  16                                    2.30  10       2.38       4       2.41  12                                    2.28  12       2.30      10       2.37   2                                    2.20  38       2.28      12       2.35   2                                    2.12   2       2.20      43       2.30   9                                    2.04  10       2.15       3       2.27  11                                    2.01   4       2.12       2       2.20  32                                                   2.04       8       2.18   3                                                                      2.12   3                                                                      2.04   8                                                                      2.01   4                                     ##STR1##                                                                     0.35       0.32             0.47                                               ##STR2##                                                                     157        146              163                                               ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        XRD patterns of dried samples                                                 EC-19      Comparative Example O                                                                          Example 17                                              Relative           Relative       Relative                              d(Å)                                                                            Intensity                                                                              d(Å)  Intensity                                                                              d(Å)                                                                            Intensity                             ______________________________________                                        15.7  63       15.9      66       15.8  81                                    7.90   4       9.21       2       9.15   2                                    7.49  19       8.00       4       7.93   6                                    5.99  34       7.54      24       7.51  21                                    5.80  16       6.02      28       6.00  31                                    *4.58 59       5.84      13       5.81  13                                    4.41  22       *4.60     63       *4.59 56                                    4.33  18       4.42      19       4.41  19                                    *3.91 86       4.34      13       4.33  18                                    3.80   8       *3.93     95       *3.92 83                                    *3.65 43       3.81       9       3.81   7                                    *3.47 59       *3.66     46       *3.66 48                                    3.39   5       *3.49     72       *3.48 64                                    *3.28 41       3.41       5       3.40   6                                    *3.18 100      *3.29     40       *3.28 40                                    *3.07 70       *3.19     100      *3.18 100                                   3.00  12       *3.07     78       *3.07 70                                    *2.91 87       3.01      10       3.01  11                                    2.86   6       *2.92     96       *2.91 71                                    2.83   6       2.84       8       2.86   7                                    2.79  11       2.62      30       2.84   7                                    2.73   2       2.55        3      2.79  11                                    2.67  23       2.51      20       2.67  20                                    2.65  56       2.48      23       2.65  48                                    2.62  31       2.43      20       2.62  33                                    2.55   6       2.42      15       2.55   4                                    2.50  17       2.38       3       2.50  16                                    2.47  22       2.30      10       2.47  21                                    2.43  20       2.28      15       2.43  18                                    2.41  13       2.20      44       2.41  12                                    2.37   3       2.15       3       2.30  10                                    2.35   3       2.12       2       2.27  12                                    2.30  12       2.04       9       2.20  36                                    2.27  13       2.01       3       2.15   3                                    2.20  37                          2.12   3                                    2.12   4                          2.04   8                                    2.04  10                          2.01   4                                    2.00   5                                                                       ##STR3##                                                                     0.33       0.31             0.44                                               ##STR4##                                                                     153        146              164                                               ______________________________________                                    

I claim:
 1. A process for the aromatization of non-aromatic hydrocarbonsin which the hydrocarbons are contacted with a catalyst comprising acatalytically active metal on a catalyst base, the catalyst basecomprising a zeolite having an X-ray diffraction pattern obtained fromCuKα radiation with the significant d values set out in Table Ahereinbefore and comprising highly crystalline crystallites having atleast 50% of its crystallites in the form of distinct circular cylinderswith an aspect ratio of at least 0.5 with a mean diameter of at least0.5 micron.
 2. A process according to claim 1 in which the hydrocarbonsare contacted at a temperature of from 430° C. to 550° C. and thehydrocarbons are a mixture of acyclic and cycloaliphatic hydrocarbons.3. The process of claim 1 or claim 2 wherein the zeolite has at least70% of its crystallites as cylinders.
 4. The process of claim 1 or claim2 wherein the cylindrical crystallites have a mean diameter of from 0.5to 4 micron.
 5. The process of claim 1 or claim 2 wherein the aspectratio of the cylinders is from 0.5 to 1.5.
 6. The process of claim 1 orclaim 2 wherein the zeolite has a composition expressed in terms of themolar ratio of oxides assuming an anhydrous state of:

    (0.9-1.3)M.sub.2 /.sub.n O:Al.sub.2 O.sub.3 :xSiO.sub.2

wherein M is a cation of valence n and x is from 5 to 7.5.
 7. Theprocess of claim 6 wherein x is from 5.7 to 7.4.
 8. The process of claim7 wherein x is from 6 to 6.5.
 9. The process of claim 6 wherein M ispotassium.
 10. The process of claim 1 or claim 2 in which thecatalytically-active metal is or includes platinum.
 11. The process ofclaim 10 comprising 0.4 to 1.2 wt% platinum.
 12. The process of claim 1or claim 2 in which the zeolite-W content is minimized in that thezeolite has an XRD pattern in which the peak height ratio (d=7.09A)/(d=3.91 A) is not greater than 0.2.
 13. The process of claim 12 inwhich the zeolite is substantially free of additional crystallinematerial.
 14. The process of claim 4 wherein the cylinders are rightcircular cylinders.